Was this external drive used on an older Mac? Or a PC?
Was the external drive encrypted? Is so by what app?
Were you using the Samsung proprietary software to manage that drive?
Disconnect all other external devices (especially drives), but connect the external Samsung SSD. Then run the following command from the Terminal app so we can the drive layout of that external drive (if other drives are attached, it just confuses things):
diskutil list external
Edit: If this was used on an older Mac, what was the OS used on that older Mac which could access that drive?